Check for oil on EFI trigger points in distributor for the missing problem. There are four of them inside clear plastic covers that you have to remove if you clean them. Each fires a pair of injectors :1&5, 4&8, 3&6, 2&7, so if missing is due to bad points, it will occur on one of these pairs.
Surging during warm-up is likely due either to improper idle speed adjustment (should be about 500-550 when in gear at normal temp) or malfunctioning auxiliary air valve. Refer to this thread:
My 72 350sl still has a problem with it's idle.